[SOLVED] Backup directory size increases a lot

Since upgraded zcs5.0.18 to zcs6.0.1 and zcs6.0.2, I observe the /opt/zimbra/backup increases a lot. Before upgrading to 6.0.1, our zcs server used disk space was 39% of total, after upgrade 6.0.1, used disk space increased to 55%, after upgrading to zcs6.0.2, used disk space increasd to 70%. This week after a default full backup, our used disk space increases to 85%.